Monkeys can make stone tools, and it’s making us rethink human evolution

Stone flakes were ancient tools that have been regarded as the handiwork of early humans, but a new study indicates this may not actually be the case.

Published in the journal Nature, the study reported on a small group of capuchin monkeys seen making small stone flakes.

It’s not apparent the monkeys realized they were making tools, but the study team said the observations should inspire caution when analyzing stone flakes and tying them to early humans.

Stone flakes are created by whacking two stones together, which causes one stone to break in a particular way. The resulting tool that is created can be used as a knife.

Archeologists have dated stone flakes to as far back as 3.3 million years ago and primitive human ancestors like Australopithecus or Kenyanthropus. However, the study team was able to film capuchin monkeys making these supposedly ancient tools.

Trying to Pinpoint Tool Use

Study team member Tomos Proffitt, a paleoanthropologist from Oxford University, told NPR he was expecting to see the monkey use rocks to crack open nuts.

“They crack open palm nuts all the time,” Proffitt said. “So we were looking for this.”

However, the team saw the monkeys cracking rocks against rocks.

“We saw this, doing this stone-on-stone percussion, and that was quite exciting looking at the material they produced,” Proffitt said, noting that the material was stone flakes.

“It was sort of a jaw-dropping moment,” he added.

The team’s excitement was tempered a bit, however, when they realized the monkeys didn’t appear to use the tools they had created.

“We hypothesize that it’s something to do with getting minerals from the quartz because they lick the dust, they ingest it,” Proffitt said.

In their report, the study team said their observations should cause field researchers use caution and avoid confusing monkey flakes with man-made ones. Proffitt said the flakes made by early humans are “more complex than what we see with the capuchins, though they share the same basic characteristics.”

He added that there are generally clues discovered along with ancient tools that indicate they were actually used. For instance, there might be cut-marks on nearby bones.